David Spade’s trump card is his vicious wimp’s aggression, and he had half a good idea in wanting to play the white-trash idiot hero of Joe Dirt. Joe, abandoned by his parents during a 1975 trip to the Grand Canyon, is a case of arrested cultural development, a freewheelin’ relic of the born-to-ramble ”outlaw” ’70s. A janitor by trade, he drives a jalopy that’s mostly rust, wears a mullet hairdo that’s significantly bigger than his head, and is instantly transported to hog heaven by any issue of Auto Trader magazine. He might be the most fanatic roadie who ever got paid in beer cases by Lynyrd Skynyrd.

Preening, bare-chested, at a carnival in order to attract the attentions of a blond cutie-pie (played by Jaime Pressly, who was the baby-doll vixen in Ringmaster, and who’s the hottest sex bomb in Hollywood right now), Joe is so grotesque that the movie, for a moment, achieves an amusing skanky charge. Joe ends up deluded into thinking that she’s his sister, a gag that pays off much better than it did in Say It Isn’t So (the prospect of incest turns Joe on). But Joe Dirt ends up blowing its own joke. Instead of making Joe blissfully arrogant in his Southern-rock-dude myopia, it turns him into a shuffling masochistic loser, a sweetheart softie pining for his long-lost family. Spade, as a result, doesn’t really get to draw on his superiority; he’s too busy enduring abuse. At one point, Joe gets excrement poured all over his precious mullet, and that, in essence, is what the entire movie does to him. It’s easy to imagine the wicked Saturday Night Live character that Joe Dirt might have been, even as you’re stuck with this half-baked, knee-jerk gross-out, spinoff-style comedy that has already defanged him.